Rotor for an axial flow turbomachine and double nut for connecting two tie-rod elements

ABSTRACT

A rotor for an axial flow turbomachine is provided, having a number of a plurality of disc-shaped or drum-shaped rotor components and at least one pin-shaped tie-rod extending through the rotor components, wherein a counter-bearing is screwed onto each of the projecting ends of the tie-rod for axially bracing the rotor components arranged therebetween. The tie-rod has at least two axially adjacent tie-rod elements which are each connected to one another in a detachable manner by connector. Elastic stretching characteristics of the two tie-rod elements are matched to each other such that, with the rotor components being clamped between the two counter-bearings, a clamping of the counter-bearing and the connection element and the rotor components arranged therebetween is at least partially released.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2013/068505 filed Sep. 6, 2013, and claims the benefit thereof. The International Application claims the benefit of German Application No. DE 102012215886.3 filed Sep. 7, 2012. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a rotor for an axial flow turbomachine, comprising a number of multiple disk-shaped or drum-shaped rotor components and at least one tie-rod extending through the rotor components, with a counter-bearing being screwed onto each of the projecting ends of this tie-rod in order to axially clamp the rotor components arranged therebetween.

BACKGROUND OF INVENTION

Such rotors are very well known from the comprehensive available prior art relating to static gas turbines. For example, a rotor of the type mentioned in the introduction is shown in the book “Stationare Gasturbinen” [“Static Gas Turbines”] (Eds Christoph Lechner and Jorg Seume), on page 629. The rotor is designed as what is termed a disk construction, wherein the rotor disks bear blades, either for the compressor or for the turbine unit of the gas turbine, on their outer circumference. A central hollow shaft as a drum-shaped component is arranged between the compressor disks and the turbine disks. A central tie-rod extends through all the rotor components and, with the aid of two counter-bearings, the forward hollow shaft and the rear hollow shaft, clamps together the rotor components arranged between these two hollow shafts. In that context, the tie-rod is stretched elastically up to its yield point, thus clamping together the individual rotor components.

A similar construction is also possible with decentralized tie-rods, wherein for example twelve tie-rods are arranged evenly distributed at the same radius.

It is further known, from EP 2 415 967 A1, to divide the rotor—embodied with a disk construction—of a gas turbine into a compressor section and a turbine section, whose respective central tie-rod is screwed into a central shaft connecting the former two to one another. In that context, the compressor disks are clamped between a first pre-clamping screw nut—screwed onto the end—and the central shaft, and the turbine disks are also clamped between the central shaft and a second pre-clamping screw nut—also screwed onto the end, wherein the pre-clampings of the compressor section and turbine section are independent of one another.

A further disk clamping of a compressor rotor is also known from DE 10 2005 052 819 A1. According to this teaching, the multi-part tie-rod comprises two tension sleeves and a compression sleeve.

Furthermore, a double nut is known from U.S. Pat. No. 5,454,662.

It is also known to weld together the disk-shaped or drum-shaped rotor components. Even combinations of the aforementioned embodiments, in which for example the compressor rotor is welded and the rotor components of the turbine unit are clamped by means of a screwed connection with bolts at the circumference, are also known.

SUMMARY OF INVENTION

The invention has an object of proposing an alternative construction of rotors for an axial flow turbomachine. The invention has a further object of providing the components necessary therefor.

The object relating to the rotor may be achieved with a rotor according to the features of the claims. The object relating to the components may be achieved with a double nut according to the features of the claims. Advantageous configurations and refinements are indicated in the dependent claims.

The invention differs from the current embodiment of tie-rods in that the latter are of one-piece design. According to aspects of the invention, it is now provided that the tie-rod or tie-rods is or are divided axially into at least two tie-rod elements, wherein the directly adjacent tie-rod elements are in each case releasably connected to one another by a connector.

Advantageously, the rotor comprises, along its longitudinal extent, a first rotor end section, at least a further rotor section and a second rotor end section, wherein the connector, as seen axially, is arranged in one of the further rotor sections. Particular advantages are realized in the configuration in which the connector and one of the rotor components are configured such that, after the counter-bearing arranged on the second rotor end section has been released, the connector adjacent to the second rotor end section, with the counter-bearing arranged on the first rotor end section, clamps together the rotor components arranged therebetween. A particular advantage of this configuration is that, in a first assembly step, those rotor components which are threaded onto the first tie-rod element can already be clamped by one of the two counter-bearings and the connector, although the rotor is not yet completely stocked with rotor components. Only once the second or further tie-rod element has been attached are the further disk-shaped or drum-shaped rotor components to be threaded thereon, after which the second counter-bearing can then be screwed onto the end of the second or further tie-rod element, whereby all the disk-shaped or drum-shaped rotor components of the rotor can finally be clamped together. According to aspects of the invention, it is provided in that context that the clamping which acts in the interim from one of the two counter-bearings and the connector on a part of the disk-shaped or drum-shaped rotor components is then released again. In this respect, the elastic stretching characteristics of the two tie-rod elements are matched to each other such that, with the rotor components being clamped between the two counter-bearings, the initial clamping of the counter-bearing and the connector is at least partially—or entirely—released. This is of particular interest for gas turbine installations in which, instead of a welded compressor rotor, a modular rotor having a disk construction should be used, which modular rotor should further also be clamped to the turbine rotor and with the aid of tie-rods. This improves the handling of the rotor during maintenance work of an operationally stressed gas turbine and reduces the time necessary for carrying out the maintenance work, since it is not necessary to unstack the entire rotor but only the turbine-side rotor section. Particularly, the connector is designed as a screw nut into which are screwed the mutually opposing ends of axially adjacent tie-rod elements. Instead, it is of course also conceivable for the connector to be connected in one piece with one of the tie-rod elements. In other words, a tie-rod element can also have, at one end, an internal thread as the connection for screwing onto another tie-rod element.

According to a first advantageous refinement, the connector has multiple openings for guiding a fluid from one of the rotor (end) sections through to another of the rotor (end) sections. Particular advantages are realized in the configuration in which the respective connector has a circumferential shaft collar which is arranged on the circumference and in which are arranged the openings as throughflow openings for cooling fluid. When the rotor is used in a gas turbine, it is then for example possible to feed compressor air—bled from the compressor—into the interior of the rotor and to guide this air through the connector into a turbine rotor, where the cooling air can be used for cooling purposes. By using a shaft collar at the circumference of the connector, it is possible to arrange the throughflow openings, which are necessary for feeding through the fluid, on a larger radius. It is thus possible to create larger throughflow cross sections and accordingly to feed through a greater cooling air mass flow rate with low pressure losses.

Further, the connector can also be used to create a support for the tie-rod in order to reduce vibrations when the turbomachine is in operation. To that end, only a radial support for at least one of the rotor components at the relevant connector is necessary.

Particular advantages are realized in the configuration in which the rotor is designed as a gas turbine rotor, the first rotor end section is designed as a compressor rotor, the further rotor section is designed as a central rotor section and the second rotor end section is designed as a turbine rotor. In that context, the central rotor section can be formed solely from a hollow shaft or from multiple bladeless rotor disks and the rotor end sections from rotor disks. It is further provided that the double nut for connecting two tie-rod elements has, centrally between the two screw openings, an inward-oriented ring or a separating web which prevents the tie-rod elements from being screwed too far into the double nut.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail with reference to exemplary embodiments in the figures. In that context, further features and advantages are indicated in the description of the figures, in which:

FIG. 1 shows a partial longitudinal section through a rotor according to the invention for a static axial flow turbomachine;

FIG. 2 shows a detail from the longitudinal section of FIG. 1, in the region of two mutually connected tie-rod elements;

FIG. 3 shows the same detail of FIG. 2, according to an alternative exemplary embodiment;

FIG. 4 shows a connection element for connecting two tie-rod elements with a shaft collar arranged at the circumference;

FIG. 5 shows, in a perspective representation, the connection element of FIG. 4 and

FIG. 6 shows a connection element bearing radially against the rotor component, in the longitudinal section of FIG. 2.

In all figures, identical features are provided with identical reference signs.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a partial longitudinal section through the rotor 10 of an axial flow turbomachine. In the exemplary embodiment shown, the rotor 10 is configured as a gas turbine rotor, wherein the remaining constituents of the gas turbine are not represented in more detail here. The construction of the rotor 10 is fundamentally modular and is to be termed disk construction.

Consequently, the rotor 10 comprises a number of rotor disks 12, which in this case are also termed disk-shaped rotor components 14. In addition, the rotor 10 further comprises a drum-shaped rotor component 16 which in the exemplary embodiment is termed central hollow shaft 18. In addition to the central hollow shaft 18, there is also a forward hollow shaft 22, screwed onto the end of a tie-rod 20, and a rear hollow shaft 24, screwed on at the opposite end. In this case, the forward hollow shaft 22 is also termed first counter-bearing 26 and the rear hollow shaft 24 is termed second counter-bearing 28. The two counter-bearings 26, 28, with the aid of the tie-rod 20, clamp the rotor components 14, 16 together and press them securely against one another. In order to achieve this, the entire tie-rod 20 is stretched elastically by the two counter-bearings 26, 28.

According to the invention, it is provided that the tie-rod 20 comprises two separately manufactured tie-rod elements 30, 32. In the exemplary embodiment shown in FIG. 1, the tie-rod 20 also comprises a connector 34 which releasably connects the two one-piece tie-rod elements 30, 32 to one another. The connector 34 is designed as a screw nut or as a double nut which has, centrally between its two screw openings 37 (FIG. 5), an inward-oriented ring 36.

The rotor 10 can theoretically be split axially into a first rotor end section 38, a further rotor section 40 and a second rotor end section 42, wherein the connector 34, seen axially, is arranged in the further rotor section 40. In the shown gas turbine rotor 10, the first rotor end section 38 is designed as a compressor rotor 44, and the second rotor end section 42 is designed as a turbine rotor 48. In the region of the further rotor section 40, a combustion chamber of the gas turbine is arranged radially outside the rotor 10. In order, when servicing the gas turbine, to release where relevant only the rotor disks 12 of the turbine rotor 48, without at the same time the central hollow shaft 18 and the rotor disks 12 arranged in the compressor rotor 44 releasing, it is provided that, after the counter-bearing 28 arranged on the second rotor end section 42 has been released, the connector 34 adjacent to the second rotor end section 42, with the counter-bearing 26 arranged on the first rotor end section 38, clamps together the rotor components 14, 16 arranged therebetween. In order to achieve this, multiple exemplary embodiments are conceivable. To that end, FIGS. 2, 3 and 4 show various exemplary embodiments. FIGS. 2 to 4 show, in longitudinal section, a detail from the transition region between the further rotor section 40 and the second rotor end section 42. Represented are the two tie-rod elements 30 and 32 and, as connector 34, a double nut 35 connecting the two ends of the former to one another. The central hollow shaft 18 is arranged radially adjacent to the double nut 35. The double nut 35 has a conical face 50 whose gradient matches an inward-oriented face 52 of the central hollow shaft 18. In addition, a smaller shaft collar 54 is provided centrally between the two screw openings 37 of the double nut 35, the side face 56 of which collar bears against a side face 58—parallel thereto—of the central hollow shaft 18. During assembly of the rotor 10, the first counter-bearing 26 is first screwed onto the end of the tie-rod element 30. This subassembly is then set upright such that the individual disk-shaped or drum-shaped rotor components 14, 16 can be placed onto the first counter-bearing 26 from above. Then, the double nut 35 is screwed onto that end of the tie-rod element 30 which has been left free, wherein in the process the rotor components 14, 16 located between the double nut 35 and the first counter-bearing 26 are clamped together. The second tie-rod element 32 is then screwed into the double nut 35, after which the rotor disks 12 provided for the turbine rotor 48 can be threaded on and placed onto the second tie-rod element 32 from above. Finally, the second counter-bearing 28 is screwed onto that end of the tie-rod element 32 which has been left free. In so doing, the entire tie-rod 20 is stretched elastically such that the clamping of the double nut 35 or, as the case may be, of the connector 34 and the first counter-bearing 26 is released.

According to the exemplary embodiment of FIG. 2, axial bores 60 can be provided both in the central hollow shaft 18 and in the double nut 35, by means of which bores a cooling device can be guided from one rotor (end) section to another rotor (end) section.

FIG. 3 shows the same detail as FIG. 2, but in which the construction for axially clamping in the region of the double nut 35 and of the central hollow shaft 18 is slightly modified in comparison with the construction of FIG. 2. The radial overlap between the double nut and the central hollow shaft 18, required in order to establish the axial clamping, is achieved here with the use of a sleeve 62 which is arranged therebetween and is provided with a flange.

FIG. 4 shows a further exemplary embodiment for clamping the rotor components 14, 16 between a first counter-bearing (not shown in FIG. 4) and the connector 34. The connector 34 is again configured as a double nut 35 with two mutually opposite screw openings 37. A larger shaft collar 54 is provided on the outer circumference, centrally between the screw openings 37, in which collar are provided, distributed evenly about the circumference, openings 64 for guiding through a cooling fluid. The two parallel side faces 56 of the shaft collar 54 transition, via a radius, into curved, tapered flanks 57 which end at the screw openings 37. FIG. 5 shows this double nut 35 with the screw opening 37 and four evenly distributed throughflow openings 64 in a perspective representation.

In order to avoid radial vibrations of the tie-rod 20 in operation, it is possible to provide, on the casing-side face of the shaft collar 54, a circumferential groove 66 with a support wire 68 therein, with the aid of which the tie-rod 20 is supported radially on one of the rotor components, according to FIG. 6 on the central hollow shaft 18.

The exemplary embodiments of FIGS. 2 to 6 all show gas turbine rotors 10 in which the second counter-bearing 28 is not yet screwed onto the second tie-rod element 32, such that only those rotor components 14, 16 depicted to the left of the double nut 35 in FIGS. 2 to 6 are clamped with the first counter-bearing 26 and those rotor components 14, 16 depicted to the right thereof are not.

Overall, the invention thus relates to a rotor 10 for an axial flow turbomachine, comprising a number of multiple disk-shaped or drum-shaped rotor components 14, 16 and at least one pin-shaped tie-rod 20 extending through the rotor components 14, 16, with a counter-bearing 26, 28 being screwed onto each of the projecting ends of this tie-rod in order to axially clamp the rotor components 14, 16 arranged therebetween.

In order to provide a rotor 10 by means of which shorter service interval times can be achieved, it is provided that the tie-rod 20 comprises at least two axially adjacent tie-rod elements 30, 32 which are in each case releasably connected to one another by a connector 34. 

1-13. (canceled)
 14. A rotor for an axial flow turbomachine, comprising a number of multiple disk-shaped or drum-shaped rotor components, at least one tie-rod extending through the rotor components, with a counter-bearing being screwed onto each of the projecting ends of this tie-rod in order to axially clamp the rotor components arranged therebetween, wherein the tie-rod comprises at least two axially adjacent tie-rod elements which are in each case releasably connected to one another by a connector, wherein elastic stretching characteristics of the two tie-rod elements are matched to each other such that, with the rotor components being clamped between the two counter-bearings, a clamping of the counter-bearing and the connector and the rotor components arranged therebetween is at least partially released.
 15. The rotor as claimed in claim 14, wherein the rotor comprises, along its longitudinal extent, a first rotor end section, at least a further rotor section and a second rotor end section, wherein the connector, as seen axially, is arranged in one of the further rotor sections.
 16. The rotor as claimed in claim 14, wherein the connector comprises screw nuts into which are screwed the mutually opposing ends of axially adjacent tie-rod elements.
 17. The rotor as claimed in claim 16, wherein the screw nut comprises a double nut which has, centrally between the two screw openings, an inward-oriented ring.
 18. The rotor as claimed in claim 15, wherein the connector and one of the rotor components are designed such that, after the counter-bearing arranged on the second rotor end section has been released, the connector adjacent to the second rotor end section, with the counter-bearing arranged on the first rotor end section, clamps together the rotor components arranged therebetween.
 19. The rotor as claimed in claim 14, wherein the rotor comprises rotor end sections, wherein respective connectors have multiple openings for guiding a fluid from one of the rotor end sections through to another of the rotor end sections.
 20. The rotor as claimed in claim 19, wherein the respective connectors have a circumferential shaft collar which is arranged on the circumference and in which are arranged the openings as throughflow openings.
 21. The rotor as claimed in claim 14, wherein respective connectors bear radially against at least one of the rotor components.
 22. The rotor as claimed in claim 15, wherein the rotor comprises a gas turbine rotor, the first rotor end section comprises a compressor rotor, the further rotor section comprises a central rotor section and the second rotor end section comprises a turbine rotor.
 23. The rotor as claimed in claim 21, wherein the central rotor section is formed from a hollow shaft or multiple bladeless rotor disks and rotor end sections of the rotor are formed from rotor disks.
 24. A double nut for connecting two tie-rod elements of an axial flow turbomachine, which has, centrally between the two screw openings, an inward-oriented ring or a separating web, the double nut comprising a circumferential shaft collar on its outer circumference centrally between the two screw openings.
 25. The double nut as claimed in claim 24, wherein a number of axial throughflow openings is provided in the shaft collar.
 26. The rotor as claimed in claim 14, wherein the clamping of the counter-bearing and the connector and the rotor components arranged therebetween is entirely released. 